The present invention is related to bearing systems, and more particularly, to slew bearing systems.
Slew bearings are large thrust bearings common to heavy loads. Slew bearings have in the past been used in applications such as steel mills and other heavy machinery. In many instances, the slew bearing is an integral and critical component of a larger system.
Slew bearings are often installed at the base of equipment to enable rotation of a supported structure. In these installations, it has often been difficult to access directly the slew bearings for inspection, maintenance, and repair. Accessing the slew bearings often required at least some disassembly of a larger system, resulting in lost productivity and higher maintenance costs. Additionally, the difficulty in accessing the slew bearings for inspections increases the likelihood of unexpected failure. Because slew bearings are large, expensive, and require long lead times for replacement, these unexpected failures may substantially impact the overall productivity of systems utilizing slew bearings.
A slew bearing system in the past generally included roller bearings positioned between concentric rings. These prior slew bearing systems typically relied upon grease as a lubricant. The grease was channeled through ports into the slew bearing to lubricate the roller bearings and the raceways of the bearing rings. In one example, an automated lubrication system injected grease at regular intervals into the slew bearing.
Prior slew bearing systems employing grease lubrication had several drawbacks. When grease was injected into the slew bearing system, excess grease within the slew bearing was allowed to escape. The exiting grease collecting around the slew bearing collected dust and created a risk of fire especially in high temperature environments such as steel mills. The grease may not adequately reach all of the bearing elements within the slew bearing system leading to wear and other damage and premature failure of slew bearing systems. Also, grease is generally pressurized during injection into the slew bearing, but resides in the bearing under low pressure and may harden. Hardened grease within the slew bearing has further prevented adequate distribution of lubricant to all of the bearing elements leading to wear and damage in the bearing and premature failure of the bearing. In addition, the input ports where the grease is delivered to the bearing system may become blocked and prevent the grease from entering the slew bearing.
Furthermore, even when properly lubricated, metal particles may be produced within slew bearings due to wear between the roller bearings and the raceways. Slew bearings have also often been employed in operating environments where external contaminants may enter the slew bearing. Slew bearings even with proper grease lubricant have been damaged internally by these various forms of contamination. Grease lubricants have tended to hold metal particles and other contaminants, resulting in those contaminants being drawn into contact with the bearing elements within the slew bearing system. Contamination within the bearing has led to increased friction diminishing the effectiveness of the slew bearing, as well as mechanical damage such as spalling and brinneling in the bearing. Grease lubricants have not typically been filtered in service and therefore contaminants have tended to collect over time increasing the potential for damage and resulting in additional failures of slew bearing systems.
Another drawback to grease lubrication has been increased heat within the slew bearings. Effective grease lubrication often required filling the interstices and internal volume of the slew bearing system. The grease typically did not flow through the slew bearing system during normal operation. These factors often lead to the slew bearing system running hotter than desired resulting in increased metal fatigue and more rapid failure of the slew bearing systems.
Grease lubricants have also led to increased clean up costs. The grease used in prior systems may be delivered to the slew bearing periodically resulting in used grease being forced out of the slew bearing system. The used grease tended to build up and maintenance was required to remove the excess grease. This clean up added to maintenance costs.
The grease lubricants used in prior slew bearing systems have also been expensive. Many applications required specialized grease to accommodate for the temperature and operating environment where the slew bearing system was employed. Also prior slew bearing systems have not been able to recycle the used grease resulting in increased operating costs for the slew bearing system. The disposal of used grease has also been costly and often required special disposal procedures to comply with environmental regulations.
The drawbacks of grease lubrication limited the life expectancy of slew bearing systems. The life expectancy of slew bearing systems has typically been calculated based upon factors such as the required load carrying capability, the effectiveness of grease lubrication, and the operating temperatures. These problems associated with grease lubrication limited the projected life expectancy of slew bearing systems, as well as increased the risk of actual failures of the slew bearings. In some applications, replacement of slew bearings has been required at regular intervals, in some cases as frequently as every few months. Given the cost of the slew bearing systems and the difficulty of installation, regular replacement of the slew bearings substantially increased overall operating costs for the slew bearing systems and reduced the productivity of the equipment and systems utilizing slew bearings.
Other prior slew bearing systems have employed oil circulation lubrication. These systems have typically filled the slew bearing with circulating oil, which may or may not be filtered and recycled. Due to the size of slew bearings, slew bearings employing oil circulation lubrication have generally required large quantities of oil. In many instances, special oils have been required due to the operating environment of the slew bearing resulting in higher material costs. In any event, special procedures where often required to dispose of the used oil, further increasing the operating costs of these slew bearing systems. Excess oil within the slew bearing has impeded the movement of the roller bearings within the slew bearing system decreasing the effectiveness of the slew bearing. Another drawback of oil circulation lubrication has been increased heat with the slew bearing. As with grease lubrication, excess heat within the slew bearing system has resulted in increased metal wear and metal fatigue, and hastened the failure of the slew bearing systems.
In light of the drawbacks associated with these prior lubrication techniques, there continues to be a need for slew bearing lubrication systems that provide proper lubrication of the bearing elements while improving reliability, extending bearing life, and reducing operating costs.
A slew bearing system is presently disclosed that comprises a first bearing ring and a second bearing ring concentrically positioned relative to each other forming at least upper and lower raceways there between, a plurality of bearing rollers positioned in each raceway between the first bearing ring and the second bearing ring, a plurality of delivery nozzles capable of delivering an air and oil mixture into the raceways adjacent the upper raceway, passages capable of fluidly communicating the air and oil mixture through the raceways and collecting some oil from the mixture adjacent the lower raceway, seals capable of regulating air flow through the passages and inhibiting outflow of oil from the raceways, and at least one exit port capable of outward flow of air and oil from the raceways adjacent the lower raceway.
Also disclosed is a slew bearing system that comprises a first bearing ring and a second bearing ring concentrically positioned relative to each other forming at least upper and lower raceways there between, a plurality of bearing rollers positioned in each raceway between the first bearing ring and the second bearing ring, a plurality of delivery nozzles capable of delivering an air and oil mixture into the raceways adjacent the upper raceway, passages capable of fluidly communicating the air and oil mixture through the raceways and collecting some oil from the mixture adjacent the lower raceway, at least one exit port capable of outward flow of air and oil from the raceways adjacent the lower raceway, an upper seal positioned between the first bearing ring and the second bearing ring, a lower seal positioned adjacent the first bearing ring capable of preventing outflow of air and oil from the passages through the bearing rings, a seal ring positioned adjacent at least one surface of the second bearing ring, and an air pressure control valve positioned adjacent the seal ring capable of regulating air flow in the passages.
Also disclosed is a method of detecting wear of a slew bearing system that comprises assembling a slew bearing system that comprises a first bearing ring and a second bearing ring concentrically positioned relative to each other forming at least upper and lower raceways, a plurality of bearing rollers positioned in each raceway between the first bearing ring and the second bearing ring, and an index system having a first reference connected with the first bearing ring and positioned relative to a second reference on the second bearing ring to provide a measurable distance between the first reference and the second reference, where the measurable distance changes with wear of the slew bearing system; and monitoring a change in the measurable distance between the first reference and the second reference to monitor wear of the slew bearing system.
Also disclosed is an index system having the capability of detecting wear of a slew bearing system comprised of a first bearing ring and a second bearing ring concentrically positioned relative to each other forming at least upper and lower raceways, a plurality of bearing rollers positioned in each raceway between the first bearing ring and the second bearing ring, and a first reference connected with the first bearing ring and positioned relative to a second reference on the second bearing ring providing a measurable distance between the first reference and the second reference, where the measurable distance is capable of changing with wear of the slew bearing system.